Abstract

Total Chilean hake (Merluccius gayi) landings from off central Chile (33°-39°S) declined from 120,000 t in 2004 to 40,000 t in 2007. This paper evaluates the impacts of both fishing and Dosidicus gigas predation relative to the observed collapse of M. gayi. We provide a brief review of the state of M. gayi stock using population indicators. In addition, we evaluate the predatorprey interaction between D. gigas and fishing to explain changes observed in the M. gayi stock in recent years using a dynamic food web model. Estimates of predation mortality suggest that cannibalism in M. gayi is more important than predation by D. gigas. In addition, a decline in length at catch, in the proportion of mature females, and in the catch per unit of effort in the M. gayi fishery has been observed since summer 2000, i.e., three years before the outbreak of D. gigas in central Chile.We projected the M. gayi biomass using two Ecopath models describing the system in 2000 and 2005 and the software Ecopath with Ecosim. The increase in D. gigas biomass resulted in a slow decrease in M. gayi biomass from 2000 to 2010. Fishing scenarios resulted in a decrease in M. gayi biomass from 2004 (juveniles) and from 2003 (adults).